Ray, the easiest way to get into the radio biz is to buy an undeperforming radio staion and change the format of that station to a more popular genre.
You can go to
http://www.radioandrecords.com/ and check out the latest deals. Also in the print version there's a listing of stations for sale. It also has a listing of ratings in every US market.
Also rememeber, with the new HD radio initative, you can even buy an AM in a market and in 5 to 7 years or so make it as viable as an FM.
Don't try to buy a popular station. The P to E ratio is so lopsided now a days that it's not worth it. Especially considering the info about HD I just gave you.
Here's a couple more links for you to check out.
http://www.nab.org/
http://www.allaccess.com/
Good luck.